Method and apparatus for thermal evaporation



May 29, 1956 J. c. OGLE, JR 2,748,026

METHOD AND APPARATUS FOR THERMAL EVAPORATION Filed March 26, 1953 5 Sheets-Shea. 1

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.7 a/mw. C? 6e, c M y 2 zaduflwz A T TOR NEW United States. Patent METHQD AND APPARATUS FOR THERMAL EVAPORATION James C. Ogle, .lr., Tarenturn, Pa., assignor to Libbey- OWens-Fortl Glass Company, Toledo, Ohio, a corporation of Ohio Application March 26, 1953, Serial No. 344,755

13 Claims. (Cl. 117-45) This invention relates broadly to the application of multiple coatings of thermally evaporable material onto a support body. More particularly, it relates to an improved method and apparatus for successively depositing multiple coatings by thermal evaporation in a vacuum chamber without the necessity of breaking the original vacuum created therein.

The process of thermal evaporation in which a source of suitable thermally evaporable material is initially placed within a vacuum chamber and spaced from a support body of glass or the like is well known in the art. According to this process, the source of material which is to form the coating is supported on a heating element in an unobstructed position opposite and facing a surface of the support body to be coated and is heated by said heating element to cause said material to be evaporated and deposited on said surface as a coating after the creation of a suitable vacuum in said chamber.

According to the above described process, the coating thickness deposited on said surface is dependent upon the amount of material evaporated by said heating element as well as the spacing between said element and said support body surface. When the material to be evaporated is supported on only a single heating element, a uniform coating is not produced as all points of the support body surface are not equally spaced from said single heating element. However, by the use of a plurality of heating elements, each of which is loaded with apredetermined weight of the same material and arranged in predetermined grid fashion in a plane parallel to and equally spaced from the support body surface, as shown for example by Strong on pages 177-179 of Procedures in Experimental Physics, it is possible to secure a coating of uniform thickness over all of said surface by the firing of all of said heating elements.

According to the present invention, in the successive depositing of multiple coatings an arrangement of heating elements as above described is required for the material forming each of said coatings in order to secure either uniform coating thicknesses or deliberate predetermined and reproducible non-uniform coating thicknesses. Thus, as used in the description and claims of this invention, a source of thermally evaporable material includes one or more pieces or particles of said material supported on a plurality of heating elements arranged in the manner described to produce either a uniform coating or a predetermined non-uniform coating of said material. It will be understood, therefore, that in the depositing of successive multiple coatings by thermal evaporation from successively fired sources, each of said sources may constitute a plurality of heating elements supporting predetermined weights of the material which is to form an individual coating.

Many uses have arisen for articles of glass or other refractive material having multiple coatings or films on a surface thereof such as, for example, dichroic and beam splitting mirrors, filters or the like. Such multiple coath 2,748,025 Patented May 29, 1956 ings comprise two or more coatings of different materials by means of which the optical characteristics of the aforementioned articles may be controlled over a wide range. The depositlon of each coating involves, of course, a separate and independent firing operation.

It is an object of this invention to provide an improved l ethod and apparatus for applying multiple coatings of predetermined thicknesses by means of which both time and expense may be saved.

Another object of this invention is to provide a method of successively applying multiple coatings of the type described during the creation of a single vacuum.

Still another object of this invention is to provide a thermal evaporation apparatus by means of which a plurality of coatings of different thermally evaporable materials may be successively deposited on a support body without the necessity of breaking the original vacuum created in said chamber.

Still another object of this invention is to provide a method of simultaneously applying coatings of the type described onto each of a plurality of support bodies.

Still another object of this invention is to provide an apparatus by means of which a multiple coating of the type described may be applied to each of a plurality of support bodies during the creating of a single vacuum.

Other objects and advantages of the invention will become more apparent during the course of the following description when taken in connection with the accompanying drawings.

According to this invention, a plurality of coatings of thermally evaporable material may be successively deposited on the surface of one or more support bodies by the thermal evaporation of successively fired sources of said material, each of which, at the time of firing of the same, is located in the same predetermined spacing away from and relative position with respect to any given point on said support body surfaces such that each of the successive coatings formed is of equal relative proportional thickness at any of said given points. This method is carried out by sequentially moving the surfaces of the support bodies to be coated into said predetermined position with respect to each of said sources of thermally evaporable material, which sources are first fixed and located in predetermined relation with respect to one another, said movement being equal to the distance and in a direction similar to that between a just-fired source and a source which is to constitute the next coating to be deposited.

That is, one or more support bodies are mounted inside a conventional vacuum chamber and are located in predetermined relation with respect to and spaced from a plurality of sources of the thermally evaporable material desired in the formation of the multiple coatings for said bodies. Each of said sources is arranged on suitable heating means in predetermined spaced relation with respect to one another and means are provided for successively and sequentially moving said bodies into a predetermined position opposite each of said sources so that a coating of material from each of said sources may be deposited on said support bodies. At each of said positions, the particular source oppositely disposed in said predetermined position with respect to said bodies is evaporated in the conventional manner above noted. However, according to this invention, the vacuum originally created in the chamber prior to the evaporation of the first source may be used during the evaporation of each of said sources. This is made possible by the novel apparatus of this invention wherein the support bodies may be moved relative to the sources of thermally evaporable materials by actuating mechanism located either outside or inside of said vacuum chamber.

In the accompanying drawings, wherein like numerals are employed to designate like parts throughout the same:

Fig. 1 is a perspective view of the overall apparatus of this invention with the vacuum chamber shown in phantom;

Fig. 2 is a plan view of the apparatus with the top of the chamber cut away;

Fig. 3 is a vertical sectional view of the apparatus taken substantially along the line 33 of Fig. 2;

Fig. 4 is a detailed horizontal sectional view of means for holding the support bodies;

Fig. 5 is a vertical sectional view of the support body holding means taken substantially along the line 5-5 of Fig. 2;

Fig. 6 is an enlarged side view of the drive means and metering device for the support body holding means;

Fig. 7 is a detailed vertical sectional view of the drive means taken substantially along the line 7-7 of Fig. 6;

Fig. 8 is a detailed view of the metering device taken substantially along the line 8--8 of Fig. 6; and

Fig. 9 is a diagrammatic view showing a manner of producing both uniform and predetermined non-uniform coatings.

In U. S. Patent 2,410,720, granted November 5, 1946 to G. L. Dimmick, there is disclosed a means for evaporating successive multiple coatings onto a plurality of support bodies. According to the method disclosed therein, the sources of material forming said coatings may each be successively moved into a centrally located position with respect to said support bodies and fired when so located. It will be noted that only three of said sources are shown, and it is apparent that at best only a few more could be added. In order to bring each individual source into the centrally located firing or evaporating position, electrical connections must be made and broken, thereby resulting in a great real of wear. In addition, due to the high temperatures generated when each evaporating boat is heated, the contact blades soon become warped and the electrical contacts eventually fail to operate. Since the failure of any contact spoils the evaporation run, it has been found that where many coatings are involved the above described apparatus is especially unreliable.

It has also been found that the movement and jarring of apparatus similar to that disclosed by Dimmick, as the boats are moved into place and the switches are closed or broken, causes particles of the sources of thermally evaporable material contained therein to be lost. This loss of material leads to varying uncontrolled coating thicknesses since all of the material must be evaporated to produce the desired thickness coating, which is predetermined by the weight of material contained in the boats. Thus, in a second way the apparatus of the aforementioned patent has not been found generally satisfactory Where large numbers of coatings are to be deposited.

it will be appreciated that by means of the apparatus disclosed in the aforementioned patent, Dimmick was primarily concerned with coating lenses or other small articles. Thus, the patentee was not concerned with the problems inherent in the deposition of the large number of successive coatings frequently necessary in the production of modern dichroic mirrors, filters or the like. Nor was the patentee concerned, in the coating of relatively small objects, with economy of space which becomes a major consideration in the coating of large articles. In addition, the apparatus of the aforementioned patent necessarily required the use of shutter means in the production of uniform coatings. Still further, said apparatus has been found particularly unsuitable for the production of coatings of predetermined non-uniformity often desired in interference colored mirrors.

On the other hand, I have found it desirable to move the support body in spite of its large area and weight rather than the sources of thermally evaporable material since the movement of said support body may be positively controlled and the extent thereof may be made .4 in accordance with the spacing between said sources as originally set up. In this manner, positive and fixed electrical connections may be made prior to each run such that the sources will be free of vibration or shock which might cause the losses of material inherent in prior art methods.

Referring now particularly to the drawings, the overall apparatus of thi invention, as best shown in Fig. 1 and designated in its entirety by the numeral 10, includes a vacuum chamber or hell jar 11 (shown in phantom in Fig. l) and a stand 12 for said chamber. Disposed within the chamber 11 are material evaporating means 13, support body holding means 14 at opposite sides of the evaporating means, and drive means 15 for moving the holding means with respect to said evaporating means. Flat glass sheets G are held by the support body holding means 14 in properly disposed position with respect to the sources S, S, and S of thermally evaporable material supported on the evaporating means 13.

The stand 12 comprises a bed plate 16 supported on legs 17 and recessed as at 18 on its upper surface to receive the lower edge of the vacuum chamber 11. When received in the recess 18, the chamber 11 may be sealed thereto in air-tight relation by suitable packing means (not shown) and the inside of the chamber may be evacuated through a central opening 19 in the bed plate 16 by suitable pump means (not shown), as well known in the art.

The material evaporating mean 13 includes oppositely disposed lead rods 29 electrically connected through vacuum-tight openings 21 in the bed plate In. Filaments 22 for each of the sources S, S and S are carried between opposite pairs of the lead rods Zii at the desired elevation by connectors 23 adjustably slidable on said rods. It will be noted from Figs. 1 and 2 that the electrical lead-through openings 21 are disposed substantially circumferentially on the bed plate 16 such that each of the opposite pairs of the lead rods can be disposed diametrically opposite one another and outwardly of the unobstructed area in the chamber between the sources of material and the glass sheets G. By means of the connectors 23, each of the filaments 22 may be adjustably positioned in aligned and properly spaced relation one above the other.

Thus, each of the filaments 22 is provided with separate and independent leads whereby each may be selectively actuated by suitable electrical apparatus (not shown) and caused to evaporate the sources of material S, S and 8" supported on the coils 23 of said filaments. As well, it will be understood that each of the filaments may be located in the desired spaced relation with respect to one another as well as in an aligned position equally spaced from the glass sheets G.

It will be further understood that while, for the purposes of illustration, each source is shown as being made up of only one filament coil or heating element, in practicing this invention a plurality of the filament coils would be arranged in grid fashion so as to support predetermined weights of the individual source of material as hereinbefore mentioned. In any case, however, regardless of the number and arrangement of filaments each source would be individually and selectively evaporable by means of the oppositely disposed pairs of lead rods 20 between which said filaments are carried. Thus, for all practical purposes, a large number of sources could be mounted within the chamber.

Each support body or sheet of glass G is held with a surface thereof to be coated in spaced and oppositely facing relation with respect to the sources of material by means of substantially rectangular frame members 24. Each of the frame members comprises upper and lower lateral bars 25 pivotally connected at opposite ends to sleeves 26 which are operably engageable with and driven in defined vertical paths by a portion of the drive means 15, in a manner to be described hereinafter. The sleeves 26 at opposite sides of the frame members are connected in fixed spaced relation by vertically extending links 27.

Each of the upper and lower lateral bars 25 is slotted longitudinally as at 28 to receive, respectively, spaced upper and lower sheet edge gripping means 29 and 30.

Each of the lower edge gripping means 30 is composed of a T shaped finger member recessed along its upper edge at 31 (Fig. 5) to engage and support said lower edge of glass sheet G. A tongue 32 on the lower edge of each of the finger members is adapted to be snugly received in one of the slots 28 whereby said finger is maintained in engagement with said lower sheet edge. Arms 33 are secured to the upper lateral bar 25 adjacent each of the slots 28 and pivotally carry from their lower ends an L shaped finger member 34 which is recessed as at 35 to engage the upper edge of the glass sheet G. A pin 36 is adapted to be snugly received in each of the slots in the upper bar so as to bear against the upper edge of the finger member 34 in holding the same in engagement with upper edge of the glass sheet. As best shown in Fig. 5, the upper end of the finger member 34 is finished at 36 (Fig. 5) to abut against upper lateral bar 25 when the glass sheet G is removed from the frame member 24.

It will be appreciated that while the glass sheets will be securely held by the frame members 24, rapid loading and unloading thereof is made possible by the arrangement above described. That is, in the loading operation, initially the lower edge of the glass sheets may be located in the recesses 31 in the lower edge gripping fingers 30 and the upper edge then swung into position in the recesses 2E5 of the upper edge gripping fingers 34. In the unloading operation, the upper fingers need only be raised slightly on their pivotal connections with the arms 33 and the sheet then swung out of position.

The drive means 15 includes vertically extending Acmethreaded shafts 37 disposed within the chamber 11 and arranged in pairs at each side of the material evaporating means 13 in position to mount the sleeves 26 of the frames 24. More specifically, Graphalloy type nuts 38 are held captive within the sleeves 26 by keys 39 (Fig. 4) and mesh internally with the threaded shafts 37 to transmit vertical movement to said sleeves upon rotation of said shafts.

Each of the shafts 37 extends below the bed plate 16 and is provided with a bevel gear 40 whereby each may be driven by horizontally extending shafts 41. As best shown in Fig. 3, the aforementioned opposite pairs of vertical shafts 37 for the frames 24 maybe driven in unison by the horizontal shafts 41 through bevel gears 42 at opposite ends of said horizontal shaft which mesh with the bevel gears 40. A common drive is provided for the shafts 37 and 41 by a drive shaft 43 at one side of the bed plate 16 and extending transversely of the frames 24 and horizontally extending shafts 41.

This drive shaft 43 has bevel gears 44, at spaced intervals opposite each of the horizontal shafts 41, which mesh with similar gears 45 on shafts 46 aligned with said horizontal shafts. Bevel gears 47 on the opposite inner ends of the shafts 46 mesh with the gears 40 on the vertical shafts 37 at one side of the opposite pairs thereof. The drive shaft 43 is driven by and removably coupled to a reversible motor 48 (not shown in Fig. 1). Thus, the vertical shafts 37 are driven in unison by the motor 48 so as to raise and lower the oppositely disposed frames 24 in a controlled manner and for a purpose to be de scribed hereinafter.

The shafts 37 are maintained vertically by columns 49 secured to and upstanding from the bed plate 16. A column is disposed adjacent each of said shafts and is connected by a flanged plate 50 to the upper end of its respective shaft 37 which end is journaled in said plate. A shield 51 may be bolted to each of the columns 49 and extended the entire height thereof so as to protect the threads of adjacent shaft from the material being evaporated. As best shown in Fig. 4, this shield projects laterally of the column and is turned-in to partially encircle the shaft 37 with respect to the material sources S, S" and 8".

As best shown in Fig. 7, the bed plate 16 is provided with openings 52 through which the lower ends of the vertical shafts 37 may be freely extended, and gland 53 and bearing 54 are provided at said openings to seal the same substantially air-tight. The gears 40 are keyed to the lower end of each of said shafts in position to mesh with the gears 42 of the shafts 41 and gears 47 on the shafts 46. As shown in Fig. 3, the horizontal shafts 41 are supported along their lengths by hearing brackets 55 secured to the bottom of the bed plate 16.

A housing 56 is provided beneath the bed plate for each of the horizontal shafts 41 and the gears 40, 42 and 47, as best shown in Fig. 3, and extends longitudinally of its respective shaft, as shown by the broken lines of Fig. 2. Each of the housings 56 is supported by hanger members 57 depending from said bed plate which further serve to maintain said housings in tight air-tight engagement with the bottom of the bed plate 16.

The shafts 46 extend outwardly from the housings 56 through an opening 58 in the side of each. Gland 59 and bearing 59 at the opening 58 serve to support the ends of the shafts adjacent the bevel gears 47 and further to provide an airtight seal for said openings. As a further sealing measure, a gasket 60 (Fig. 7) may be provided between said housings and the base plate. Thus, it will be seen that sufficient sealing means are provided for insuring the maintenance of a vacuum within the chamber 11.

Brackets 61 and 62 are secured to the sides of the bed plate 16 for supporting bearing plates 63 for the ends of the shafts 46 adjacent the bevel gears 45. Flanges 64 on the bearing plates 63 are provided with bearing openings for supporting the drive shaft 43 adjacent the bevel gears 44 which mesh with the aforementioned gears 45 on the shafts 46. Adjacent the flange 64, the drive shaft 43 is coupled at 65 to the output shaft 66 of the reversible motor 48. The motor is supported on a ledge 67 carried from the bed plate 16 by the bracket 62 and another bracket member 68 on an adjacent side of said bed plate.

Disposed between the shafts 46 and along the drive shaft 43 is a metering device, indicated in its entirety by the numeral 76, which serves to indicate the position of the frames 24 on the vertical shafts 37 within the vacuum chamber 11. The metering device 69 includes a block member 70 received on a threaded length 71 of the drive shaft 43 and having secured thereto a pointer 69. As best shown in Fig. 8, the block member and pointer are caused to move along the length of the drive shaft during rotation thereof by means of a finger 73 extending laterally from said block member and slidably received between spaced guides 74 mounted upon and extending longitudinally of a bracket 75 carried by the bed plate 16.

A scale 76 is mounted on the side of the bed plate and above the bracket 75 in position to extend beneath and longitudinally of the path of the end of pointer 72. The scale may be divided into suitable increments, as shown in Fig. 1, such that the position of the frames 24 relative to their upper and lower limits of movement within the vacuum chamber 11 are indicated by the position of the pointer 72 above said scale. That is, during rotation of drive shaft 43, in moving the frames 24 vertically within the chamber, the block and pointer are caused to move proportionately along said shaft. The upper and lower limits of movement of said frames are controlled by micro-switches 77 carried by the bracket 75 at each end of the scale 76. Activating rollers 78 are carried by arms 79 on the switches in position to be engaged by the finger 73 at said limits of movement.

The metering device 76 may be enclosed within a housing 80 carried by the bed plate 16 (as shown in Fig. 1'

and. indicated by the phantom lines of Fig. 2) for protecting the parts of said device. A window 81 may be provided in the top of said housing above the scale 76 to permit observation thereof.

Dealing now with the novel method of successively applying multiple coatings of thermally evaporable material onto support bodies according to this invention, and with particular reference to the above described apparatus, a plurality of sources of thermally evaporable material, such as S, S" and S'", are arranged centrally of the vacuum chamber 11 and in a predetermined spaced relation on the filaments 22. As hereinbefore mentioned, each of the sources is shown diagrammatically in Fig. 1 as being supported on the coils of a single filament. As explained, however, it is contemplated that each source would comprise a plurality of individual predetermined weights of the same supported on filaments arranged in a predetermined grid fashion so as to produce either uniform or predetermined non-uniform coatings on the support bodies.

That is, the groups of filaments for each source of material are arranged in predetermined relationship with one another. For example, as shown in Fig. 9, the source S of thermally evaporable material may be made up in part of spaced weights of said material, each of which is arranged in predetermined relation with respect to corresponding spaced weights of the thermally evaporable material of sources S" and 8". Thus, if the spaced Weights of the source S were each lowered the distance 1, each of the same would be disposed in superimposed relation with respect to said corresponding weights of the source S".

The support bodies, such as the glass sheets G, are then disposed in oppositely facing relation at both sides of thethermal evaporation sources. In this respect, it will be understood that the frames 24 are adapted to support glass sheets of widely varying sizes. However, in accordance with this invention, each of said oppositely facing sheets is similarly disposed with respect to the sources S, S" and 8. That is, each of the glass sheets G is equally spaced radially from the fixed sources and as well is oppositely disposed therefrom in an identical manner. This arrangement then permits the glass sheets G to be simultaneously moved into properly disposed position with respect to each of the sources so as to deposit thereon multiple coatings.

At this time, the chamber 11 may be evacuated in a manner and to a degree well known in the art. The glass sheets G may then be moved simultaneously into properly disposed position with respect to a first of the sources, the operator of the drive means for support body holding means 14 being guided by the position of the pointer 69 on the scale 73. When the sheets are so disposed, the first source, preferably one of the outermost sources S or 8", may be caused to evaporate, in a manner well known in the art and by means of the selectively operable controls hereinbefore mentioned, so as to simultaneously deposit a coating of predetermined thickness on each of said sheets.

After the deposition of the first coating and while maintaining the original vacuum created in the chamber 11, the glass sheets G are simultaneously moved into properly disposed position with respect to a second source. Of course, the distance moved will be identical to the spacing between said first and second source.

For example, if the first source to be evaporated was S and the second was to be S, the glass sheets would be moved the distance 1 as indicated in Fig. 9. Again, of course, the operator would determine the extent of said movement by means of the scale 73. At this sec ond position of the glass sheets, the second source may be selectively evaporated so as to simultaneously deposit coatings of predetermined thickness onto the first coating of said sheets. This operation may be repeated for the desired number of coatings to be deposited.

As previously mentioned, the novel method of this invention is particularly well suited to the depositing of predetermined uniform as well as predetermined, reproducible non-uniform coatings. Thus, the predetermined coatings of predetermined thicknesses, as mentioned herein, have reference to either uniform or non-uniform coatings. In the deposition of uniform coatings, the glass sheets G may be arranged in parallel planar relation with respect to aligned sources of thermally evaporable material, as shown by the leftmost sheet in Fig. 9, and caused to be maintained in said relation during movement into properly disposed position with respect to each of the several sources. On the other hand, in the deposition of non-uniform coatings, the glass sheets may be arranged in a predetermined non-parallel planar relation with respect to said sources, as shown for example by the rightmost sheet in Fig. 9. In being moved from one position to another opposite each of the sources, the sheets would be maintained in said predetermined non-planar relation with respect thereto such that, similar to the uniform coatings, each of the successive nonuniform coatings formed is of equal relative proportional thickness at any given point on the coated surface of each of said sheets.

It will be noted that while the glass sheets G are moved while disposed in said non-parallel relation with respect to said sources, each point on said sheets is moved in a parallel planar path with respect thereto. Thus, it will be understood only a slight modification of the support body holding means 14 from the design illustrated in the drawings would be required.

It is to be understood that the form of the invention disclosed herein is to be taken as the preferred embodiment thereof, and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the following claims.

I claim:

1. In apparatus for applying multiple coatings of thermally evaporable material to a support body, a vacuum chamber, means for fixedly mounting a plurality of sources of said material in said chamber in predetermined spaced relation to one another, means in said chamber for holding said support body in spaced relation to said sources so that the surface thereof to be coated is opposite and facing the said sources, and means for moving said support body relative to said sources while maintaining the vacuum in said chamber, said lastmentioned means being operable to intermittently and successively move and locate the holding means for said support body in a definite predetermined position opposite each of said sources.

2. In apparatus of the character defined in claim 1, plus means for independently and selectively evaporating each of said sources of thermally evaporable material.

3. In apparatus for applying multiple coatings of thermally evaporable material onto a surface of a support body, a vacuum chamber, means in said chamber for fixedly mounting a plurality of sources of said material along a defined contour in predetermined spaced relation with respect to one another, means for holding said support body within said chamber with the surface thereof to be coated facing and opposite said sources, and means for moving said support body holding means along a defined path parallel to the defined contour of said source mounting means, said last-mentioned means being operable to sequentially and successively locate the support body holding means in a predetermined position opposite each of said sources.

4. In apparatus of the character defined in claim 3, plus means for independently and selectively evaporating each of said sources of thermally evaporable material.

5. In apparatus for simultaneously applying multiple coatings of thermally evaporable material to a surface of each of a plurality of support bodies, a vacuum chamber, means in said chamber for mounting a plurality of sources of said material in predetermined spaced and coplanar relation with respect to one another, means for mounting each of said support bodies in said chamber with the surface thereof to be coated facing and in equal radially spaced relation with respect to said sources and opposite the plane containing the said sources so that a line drawn through a source of coating material being activated and normal to the plane containing the said sources may pass through the surface being coated, and means for moving each of said support bodies relative to said sources in defined paths parallel to the plane of said sources while maintaining a vacuum in said chamber, said last-mentioned means being operable to sequentially and successively locate the holding means for each of said support bodies in a predetermined position opposite each of said sources.

6. In apparatus of the character defined in claim 5, plus means for independently and selectively evaporating each of said sources of thermally evaporable material.

7. In the method of applying a plurality of coatings of thermally evaporable material onto a surface of a support body, the steps of fixedly mounting a plurality of evaporation sources of said materials in spaced relation along a defined contour within a vacuum chamber, mounting said support body with the surface thereof to be coated facing and opposite a first source of material, establishing a vacuum within said chamber and evaporating material from said first evaporation source to provide a first coating on said surface, moving said support body a fixed distance along a defined path to place a portion of the surface coated by said first source opposite and facing a second source of evaporable material, said path being spaced equidistantly from said sources and parallel to the contour thereof, and thermally evaporating material from said second source onto said support body.

8. In the method of applying a plurality of coatings of thermally evaporable material onto a surface of a support body as described in claim 7, in which the fixed distance the support is moved is equal to the distance between the said sources of evaporable material.

9. In the method of applying a plurality of coatings of thermally evaporable material onto a surface of a sup- 10 port body as described in claim 7, in which the said support is moved sequentially relative to additional evaporation sources to place additional coatings thereon in addition to those placed thereon by said first and second evaporation sources.

10. In the method of applying a plurality of coatings of thermally evaporable material onto a surface of a support body as described in claim '7, in which the plurality of coatings of thermally evaporable material are applied under a single vacuum, and said support body is moved while the said single vacuum is maintained.

11. In the method of applying a plurality of coatings of thermally evaporable material onto a surface of a support body as described in claim 7, in which a plurality of support bodies are located within said chamber and are in an equal radially spaced position around said sources of evaporating material, and in which the said support bodies are moved together past said sources.

12. In the method of applying a plurality of coatings of thermally evaporable material onto a surface of a support body as described in claim 7, in which the said sources of evaporation materials are generally aligned.

13. In the method of applying a plurality of coatings of thermally evaporable material onto a surface of a support body as described in claim 7, in which said sources of evaporation material are in co-planar relation with respect to one another, and in which the surface of the support body is moved in non-parallel relation with respect to said sources and is adapted to be moved in a defined path parallel to said aligned sources to maintain said non-parallel relation therewith.

References Cited in the file of this patent UNITED STATES PATENTS 2,239,452 Williams et al Apr. 22, 1941 2,384,209 Sukumlyn Sept. 4, 1945 2,43 0,994 Reynolds Nov. 18, 1947 2,532,971 Van Leer et a1. Dec. 5, 1950 2,539,149 Miller Jan. 23, 1951 2,586,752 Weber et al Feb. 19, 1952 

7. IN A METHOD OF APPLYING A PLURALITY OF COATINGS OF THERMALLY EVAPORABLE MATERIAL ONTO A SURFACE OF A SUPPORT BODY, THE STEPS OF FIXEDLY MOUNTING A PLURALITY OF EVAPORATION SOURCES OF SAID MATERIALS IN SPACED RELATION ALONG A DEFINED CONTOUR WITHIN A VACUUM CHAMBER, MOUNTING SAID SUPPORT BODY WITH THE SURFACE THEREOF TO BE COATED FACING AND OPPOSITE A FIRST SOURCE OF MATERIAL, ESTABLISHING A VACUUM WITHIN SAID CHAMBER AND EVAPORATING MATERIAL FROM SAID FIRST EVAPORATION SOURCE TO PROVIDE A FIRST COATING ON SAID SURFACE, MOVING SAID SUPPORT BODY A FIXED DISTANCE ALONG A DEFINED PATH TO PLACE A PORTION OF THE SURFACE COATED BY SAID FIRST SOURCE OPPOSITE AND FACING A SECOND SOURCE OF EVAPORABLE MATERIAL, SAID PATH BEING SPACED EQUIDISTANTLY FROM SAID SOURCES AND PARALLEL TO THE CONTOUR THEREOF, AND THERMALLY EVAPORATING MATERIAL FROM SAID SECOND SOURCE ONTO SAID SUPPORT BODY. 